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1. Field of the Invention
The present invention relates to a method and apparatus for repairing and structurally reinforcing piling, and in one embodiment, conductor pipes in a pipe within a pipe arrangement such as typically found in an offshore marine environment.
2. General Background of the Invention
In the offshore oil and gas well drilling industry, conductor arrangements are typically used as part of a marine platform. These conductor arrangements often include a smaller diameter inside pipe contained concentrically within the bore of a larger diameter outer pipe or conductor. The inner pipe is referred to as a flow casing. The outer pipe is referred to as a conductor.
Many of these conductors extend between the ocean floor and the rig deck or cellar area. These are areas of the platform that are above the water surface. However, the conductors and flow casings must necessarily interface with the water surface where they are subjected to wave action and corrosion because of the mix of salt water and air.
Other portions of an offshore marine platform that include horizontal members, diagonal members, and inclined members can also be subjected to environmental factors that corrode or mechanically erode these portions of the platform.
Patents have issued that relate generally to the concept of a method and apparatus for protective encapsulation of structural members.
One early patent is the Papworth patent 4,068,483 entitled xe2x80x9cProtective Sheath for Water-Eroded Wood Pilingxe2x80x9d. In the Papworth patent, the sheath is for a water-eroded wood piling. The sheath is a longitudinally split, flexible and resilient plastic casing with overlapping circumferentially end segments. The casing has a preformed, integral spout at its upper end into which wet concrete can be poured to fill the casing around the eroded section of the piling. Flexible bands clamp the casing tightly around the piling, and the spout has aligned openings in its opposite sides for passing the uppermost one of these bands. The casing may comprise two or more longitudinal sections in overlapped sealed engagement with each other end-to-end for enclosing a long eroded section of the piling.
In the Colbert patent 4,023,374, there is disclosed a repair sleeve for a marine pile and a method of applying same. The ""1374 patent discloses a preformed molded fiberglass resin plastic repair sleeve for use on a marine or other submerged concrete pile and a method of applying the same. The sleeve is provided with at least one vertical seam consisting of inside interlocking reentrant bends which together establish an interlocking tongue and groove joint. The joint is maintained effective by self-tapping screws which are in engaged relation with steel closure clips or strips. The sleeve after assembly is centered about the pile undergoing repair and the continuous space which exists between the sleeve and the pile is filled with a suitable grout which, when hardened, encompasses the internal or inside portions of the joint under pressure and prevents unfastening of the seam. The vertical longitudinal extend of the sleeve is somewhat greater than the water depth of the partially submerged pile to which it is applied and, where a cylindrical concrete pile is concerned, the sleeve is molded on an arcuate bias so as to present an open gap enabling the sleeve to be readily slipped sidewise onto the pile by one or more divers and the gap thereafter closed in order to effect the interlocked joint. Where a square pile is undergoing repair, the sleeve assumes a conformable four-sided shape or, alternatively, it may be formed of two mating right-angle sleeve sections having a pair of vertical inside interlocking joints or seams between their adjoining side margins.
The Straub patent 4,114,388 discloses a device for protecting a pile from ice formations collecting on it and subsequently abstracting the pile as a result of a variation of tide level including a tapered guard member secured to the pile. The guard member is firmly secured to the pile by interconnecting stiffening members, horizontal stiffening rings, vertical fin members and compression rings which also serve to prevent deformation of the guard member taper as a result of interaction with the ice formations. The guard member comprises two sections connected by vertically extending tongue and groove joints.
The Moore patent 4,306,821 discloses a system for the restoring and reconditioning of structural piling. The system provides an outer form which is attachable to a portion of the piling which has been eroded or corroded and has lost some of is thickness and thus its overall strength. A diameter building filler is placed into the intraform space between the form and the piling, the filler providing a protective and structural coating to that portion of the piling where corrosion or damage has taken place. In the preferred Embodiment, the filler is a setting material such as a suitable epoxy.
Three patents have issued to Richard Snow and Milton Ellisor. These patents include U.S. Pat. Nos. 4,876,896; 4,892,410; and 4,993,876. The ""896 and ""410 patents discloses a method and apparatus for forming an encapsulation or encasement about a structural member that is said to be suited for use in a marine environment. A two-component polymer system for protective and repair encapsulation is pumpable in two separate strings to the location of the structural member to be encapsulated. The two reactive components are combined in a static mixer immediately prior to be injected within the surrounding translucent jacket. By combining the reactive components immediately prior to use, premature setup is avoided and the resulting grout may be directed to flow upwardly in the jacket for enhancing final properties. By suitable coloring of the components, visual monitoring of the final mixing and distribution in the translucent form or jacket of the encapsulation material may be monitored. A field test for determining bond strength of the encapsulation polymer to the structural member is also disclosed in the ""876 patent and in the ""410 patent. The ""896 patent discloses a method of testing protective encapsulation of structural members.
The above discussed patents all relate primarily to coatings for protecting against corrosive effects of the surrounding marine environment. However, the prior art fails to address a problem of structural reinforcement for structural members that have become weak because of the corrosive and/or mechanical effects of the surrounding environment. Further, these patented prior art systems do not address concentric, pipe within pipe configurations.
The present invention provides an improved method of structurally reinforcing a single tubular member (in one embodiment) and an assembly of tubular members (in another embodiment) in a marine environment. The single tubular member (in the first embodiment) can be a pipe, pile, brace or beam at the waterline. The assembly including a smaller diameter flow casing inside of a larger diameter conductor pipe, providing an annulus in between the flow casing and the conductor pipe.
For an assembly of tubular members, the method includes first placing a plurality of lug anchor points in the annulus, in between the smaller diameter tubular member (eg. flow casing) and the larger diameter tubular member (eg conductor pipe). The annulus is dewatered to a desired elevation, using a suction pump line attached to one of the ports 14.
A volume of a first grout product (eg. urethane grout) is then pumped into the annulus at a selected, lower elevational position. The first grout product forms a floating plug.
A volume of a second grout product ((eg. polymeric, epoxy, or cementitious, preferably epoxy) is then pumped into the annulus at a position above the first grout product.
A jacket (eg. fiberglass, a composite, plastic) is then placed around the larger diameter conductor pipe.
A reinforcement cage can optionally be placed in between the larger diameter conductor pipe and the jacket.
A volume of a third grout product (eg. polymeric, epoxy or cementitious, preferably epoxy) is then pumped into the space in between the jacket and the larger diameter conductor pipe. The third grout product encapsulates the reinforcement cage, and also forms a bonded interface to both the outside surface of the larger diameter conductor pipe and the inside surface of the jacket.
The jacket preferably has multiple sections of differing respective diameters. The jacket can be plastic, fiberglass or a composite.
The jacket can have a larger diameter upper section and a smaller diameter lower section, the reinforcement being positioned next to the larger diameter upper section.
A seal can be placed at the bottom of the jacket, in between the jacket and outer surface of the larger diameter conductor pipe.
The reinforcement cage can include inclined portions and/or laterally extending portions. The reinforcement cage can be of a metallic construction such as of metallic wire including portions that are woven to form a matrix or cage that extends longitudinally and circumferentially around the conductor pipe. Alternatively, the reinforcement cage can be manufactured of plastic, carbon fiber or FRP.
The shear lugs can include a plurality of generally horizontally placed members. The shear lugs are preferably placed by supporting them from either one of the conductor pipe or the flow casing.
The lugs preferably extend radially from a position next to the flow casing to a position next to the conductor pipe.
In the preferred method, the first grout product is preferably a lighter weight, urethane grout. The second grout product is preferably a heavier grout product such as epoxy grout. The third grout product is preferably epoxy grout.
In another embodiment of the method and apparatus of the present invention, reinforcement of an assembly of an inner flow casing and an outer conductor pipe is accomplished without a reinforcement cage, wherein the annulus has been dewatered and a lower floating xe2x80x9cplugxe2x80x9d of a first grout product is positioned in the annulus between flow casing and conductor. A second, preferably heavier grout product is then placed above the plug.
A jacket is then positioned around the outer surface of the conductor pipe (see FIGS. 2-2A and 4-5). A third grout product is then injected into the space in between the jacket and the outer surface of the conductor. Optional standoffs can be used to space the jacket from the conductor pipe. A wrap (preferably carbon fiber) is then wrapped spirally around the jacket, adhered thereto with an adhesive or penetrant, and can be lowered into position if below the waterline.